While it is known that pupil size varies in its diameter in darkness between individuals from 3 mm to 9 mm, little attention has been paid to the effect of this difference on the night vision and vision in dim light (scotopic vision is dark adapted vision). Those with large pupils suffer from much more light scatter, glare, halo, and related aberrant focus of light rays that can make function under certain conditions of lighting very difficult.
Laser vision correction in particular has added new quality of vision difficulties for many of these individuals. Exposing the retina to light focusing from as much as nine times more surface area essentially magnifies every variation in curvature from the ideal. Currently, only direct acting miotic agents such as pilocarpine are used in an effort to decrease pupil size. Pilocarpine causes brow ache, ciliary muscle contraction and pseudo myopia, excessive dimness when first applied, and redness. Its effect lasts only a few hours, and it has known, though remote, risk of retinal detachment probably related to pull on the retina from stimulated ciliary muscle contraction. For these reasons it is rarely tolerated or considered a clinically useful alternative for patients with large pupils in dim light.
The only other medication used to affect pupil size is dapiprazole, an alpha-1 adrenergic receptor blocking agent. Dapiprazole is 5,6,7,8-tetrahydro-3-[2- (4-o,tolyl-1-piperazinyl)ethyl]-8-triazolo[4,3-a]pyridine hydrochloride. It is available in a 0.5% solution to partially counteract, or reverse, the dilation effect of phenylephrine, an adrenergic dilating agent, and the dilating and accommodation loss caused by tropicamide. In addition to producing redness upon instillation, dapiprazole has very little effect on pupil size in dim light in clinical application when used topically for this purpose, and therefore its sole use is as a treatment of iatrogenically induced mydriasis produced by adrenergic or parasympatholytic agents only.
The present invention is directed to a method for reducing pupil diameter in dim light in cases where dilation of the pupil is excessive, such as 6 mm or greater. In this process, the method of the invention does not induce ciliary contraction or any undesirable pseudomyopia that may result from taking certain medication. Also, by the method of the present invention, mydriasis of parasympatholytic agents is reversed similarly to dapiprazole. In fact it may be more effective on agents paralyzing accommodation such as 1% cylogyl, which can then be used for more complete cycloplegia and accurate prelaser refractive measurement.
To this date, no eye drop has been developed for the purpose of optimizing pupil size such as by reducing pupil diameter in dim light without undesirable side effects. The reason no eye drop has been successfully developed to accomplish this purpose is that no one recognized that the alpha-1 antagonists other than dapiprazole, none of which currently exists as a topical eye medication, and which are currently used for treatment of high blood pressure, treatment of pheochromocytoma, migraines, bladder spasm, prostate enlargement, and sexual dysfunction, might be adapted for this purpose.
Thus, there exists a need to provide an ophthalmic composition which achieves the combined requirements of comfort and pupil diameter optimization.
Actions of alpha adrenergic receptor antagonists include blocking alpha-1 receptor mediated contraction of arterial and venous smooth muscle. Alpha-2 adrenergic receptors are involved in suppressing sympathetic output, increasing vagal tone, facilitating platelet aggregation, inhibiting the release of norepinephrine and regulating metabolic effects. Alpha adrenergic antagonists have a wide spectrum of pharmacological specificities and are chemically heterogeneous.
Alkylating agents, imidazolines, piperazinyl quinazolines and indoles comprise the various chemical classes of alpha receptor antagonists. Many have both alpha-1 and alpha-2 receptor antagonist activity. For the present invention alpha-2 activity as represented by the indoles is of no clinical benefit. The alkylating agents offer potential for long term effectiveness for minimizing pupillary dilation, but are less effective and cause more redness than the imidazolines, such as phentolamine. The piperazinyl quinazolines, such as prazosin and dapiprazole, have modest effect on pupil diameter in dim light, but to date our research shows they are not as clinically effective as the imidazolines for this purpose. Development of longer lasting, more potent piperazinyl quinazolines may be clinically effective however. As phentolamine is not as strong an alpha-1 receptor antagonist as prazosin its stronger clinical benefit may relate to other related properties of the drug as well as its alpha-1 antagonism. These properties include blocking receptors for 5-HT, release of histamine from mast cells, and blockage of K+ channels. Phenoxybenzamine is similar in its chemical mediation.